This invention relates generally to medical devices, and more particularly, to devices for aiding surgeons in the identification of tissue to be removed from a human or veterinary patient.
It has become almost axiomatic that earlier detection of malignancies lead to improved patient survival rates. Improved mammographic techniques, for example, result in the earlier detection of smaller lesions in the breast. Accurate preoperative localization of lesions (that is, the determination of their size and position) serve two important concerns simultaneously: the successful extraction of a suspect lesion, without the removal of unduly large amounts of normal breast tissue. It may of course be desirable to locate cancerous or other tumors, foreign bodies, normal tissue structures or other objects within the body or within an organ of the body. Such locations include the liver, ductal structures, brain, lungs or other portions of a human or veterinary patient.
The localization of lesions which cannot be palpated is of particular concern, precisely since they cannot be palpated by the surgeon during surgery. Lesions may be nonpalpable because they are small in size and therefore difficult to locate (especially in large breasts), or because they are located deep within the tissue mass of the breast. Currently, such lesions are often initially located by radiology or ultrasound, and the lesion marked by a localization needle assembly prior to biopsy or surgery. Such needle assemblies have included a hypodermic needle or cannula which is inserted in the body to an area adjacent to and in contact with the lesion of interest. A marking wire (commonly referred to as a xe2x80x9chookwirexe2x80x9d or xe2x80x9chookwire-typexe2x80x9d stylet) is then inserted through the needle or cannula into the lesion and anchored in place. The needle or cannula is then removed, leaving the marking wire in place.
One highly useful device which aids in locating nonpalpable lesions within the breast is that devised by Dr. Daniel B. Kopans et al., disclosed, for example, in xe2x80x9cA Modified Needle-Hookwire Technique to Simplify Preoperative Localization of Occult Breast Lesions,xe2x80x9d D. B. Kopans et al., Radiology, March, 1980, Vol. 134, page 781; xe2x80x9cVersatile Spring Hookwire Breast Lesion Localizer,xe2x80x9d D. B. Kopans et al., American Journal of Roentgenology, March 1982, Vol. 138, pages 586-87; and xe2x80x9cSpring Hookwire Breast Lesion Localizer: Use with Rigid-compression Mammographic Systems,xe2x80x9d Radiology, November, 1985, Vol. 157, pages 537-38; all of which are expressly incorporated by reference herein. The hookwire-type stylet or localizer disclosed by Kopans et al. comprises a stainless steel wire having a hairpin hooked-end portion. In the use of a Kopans-type hookwire stylet or localizer, a hypodermic needle is initially placed into the breast to locate a lesion of concern. An attempt is made to aspirate the lesion (via syringe connected to the needle), in case the lesion is a cyst rather than a tumor. If aspiration is unsuccessful, the needle is then positioned adjacent to the lesion, and the location optimally confirmed by using two mammographic positions. When the needle is properly positioned, the Kopans-type hookwire stylet is introduced through the needle. The hook is engaged in the lesion, the proper positioning confirmed and the needle then withdrawn, leaving the stylet in position for surgery.
A preferred embodiment of the Kopans-type stylet 1 is shown in FIG. 1, sold by Cook Incorporated of Bloomington, Ind. The localizer stylet 1 is sold with a thin-wall localization needle (21, 20 19 or 18 gage) 5.0, 9.0 or 15.0 cm in length. (An embodiment having a reinforced portion 2 cm long located 1 cm from the distal tip of the stylet is sold in the same lengths, but only in 21 or 20 gage.) Suitable syringes and other surgical adjuncts are also provided in a kit containing the Kopans-type stylet. A positioning mark 2 is provided on the localizer stylet 1 to provide visual assurance that its spring-hook 3 is contained within the tip of the associated needle during manipulation of the needle. The hook 3 is simply formed by annealing the wire of the stylet 1 and bending it over itself at the annealed location.
The Kopans-type stylet is advantageous over other stylets for several reasons. The stylet is flexible and pliable, and is easily handled during the localizing procedure. Its straightforward construction permits it to be manufactured at a reasonable cost. While very useful for its intended purpose, the Kopans-type stylet is subject to a few drawbacks during use. The stylet is also occasionally subject to movement within the tissue of the patient when the patient moves or when the patient is moved, for example, during or after mammography, or during transport from the radiology lab to the operating room or surgical theater. Such migration may arise because the hook expands into the fatty tissue of the breast.
Other localization needles and devices are known, but each have their own drawbacks. They may be so large and heavy that they are subject to undesirable migration within the patient, either from movement of the patient, or transport of the patient from the location of imaging (typically a radiology lab) to the surgical theater. They may also be so large and heavy that they lack the flexibility and pliability desirable for use. Finally, they may be relatively complex in structure and unduly expensive to manufacture.
It would be highly advantageous to have localizer devices which resisted migration, and perhaps accidental transection by the surgeon during excision, yet which possessed a good degree of flexibility and pliability. It would also be highly advantageous to have such devices which were relatively straightforward in construction and were relatively inexpensive to manufacture.
The foregoing problems are solved and a technical advance is achieved in an illustrative medical device for localization, that is, establishing the location or position of tissue of surgical interest. According to one aspect of the present invention, there is provided a stylet for use with a medical device, the stylet comprising first and second wire segments each including respective distal ends and respective distal twisted portions adjacent their respective distal ends, the distal twisted portions being twisted about one another, the first wire segment further including an elongated portion extending from the proximal end of its distal twisted portion and the second wire segment extending at least partly laterally from the proximal end of its distal twisted portion and a rounded or curved portion at the distal ends of the first and second wire segments.
According to another aspect of the invention, there is provided a localizer stylet for use with a medical device, the stylet comprising: a shaft comprising first and second wire segments each including respective distal ends and respective distal twisted portions adjacent their respective distal ends, the distal twisted portions being twisted about one another, the first wire segment further including a generally straight portion extending proximally of its distal twisted portion and the second wire segment further including a hook extending proximally of its distal twisted portion, and a rounded portion over the distal ends of the first and second wire segments.
The medical devices of both aspects can most readily be understood as an improvement in Kopans-type or hookwire-type localizer stylet having the wire shaft or longitudinal segment with a distal end, the hook or second segment depending in an at least partly lateral direction from the wire shaft, or elongated wire. The specific improvement of the present invention entails spacing the hook proximally of the distal end of the wire shaft, and providing the wire shaft or segment with a twist at the distal ends. Unexpectedly, this simple expedient significantly improves anchoring of the localizer stylet within the tissue of the patient, thereby reducing the likelihood of undesired migration of the stylet when the patient moves, or is moved or transported.
In the preferred embodiment of the medical device, the localizer stylet comprises first and second wire segments, each wire segment including a distal twisted portion adjacent its respective distal end. The first wire segment extends longitudinally and proximally of its distal twisted portion, while the second wire segment extends from its distal twisted portion in a direction with a lateral component. The localizer stylet of the preferred embodiment of the present invention also includes a rounded portion, such as a bead of solder, at the distal ends of the first and second wire segments. The localizer stylet of the embodiment has several advantages over prior localizer stylets. The embodiment possesses the simplicity of construction
and use enjoyed by prior Kopans-type or hookwire-type localization devices. The potential for breakage at the bend of the prior Kopans-type stylet is avoided, because the present invention does not require any annealing of the wires making up its stylet. Perhaps most significantly, the disclosed stylet is less subject to undesirable changes in position which might otherwise be caused by transport and other movement of the patient between performance of the localization procedure and surgical removal of the tissue of interest.
xe2x80x9cTwisted about one anotherxe2x80x9d means that either or both of the portions is twisted about the other. It is likely easier to reliably manufacture embodiments in which both portions are twisted in interlocked, corkscrew shape, but the principle of the present invention is also directed to embodiments in which only one of the portions is twisted about the other. xe2x80x9cTwisted about one anotherxe2x80x9d is intended as a shorthand reference to cover both structures. Preferably, the distal twisted portions of the wire segments are twisted twice about each other, that is, at least one of them extends through a curve of about 720xc2x0.
Preferably, the hook is straight and is angled away from the generally straight portion of the first wire segment. Also preferably, the first and second wire segments are separate pieces, for example, are composed of stainless steel wire having a circular cross-section. The rounded portion over their distal ends preferably comprises a bead of solder or other suitable medical grade material.
Also preferably, the localizer stylet incorporated in the medical device of the present invention can include a reinforcement near the distal end of the stylet shaft or longitudinal segment. The reinforcement can be a thickened portion of the stylet shaft, but the reinforcement preferably comprises a cannula segment located proximal of the hook, through which the generally elongated portion of the first wire segment extends and is fixed.
As with prior Kopans-type or hookwire-type localizer devices, the medical device of the present invention also preferably comprises a needle assembly dimensioned to receive therethrough the localizer stylet disclosed above, as well as a syringe connectable to the needle assembly. The needle assembly preferably comprises a needle cannula having a proximal end, and a hub disposed about the proximal end of the needle cannula. Advantageously, the proximal end of the needle cannula extends proximally beyond the hub of the needle assembly. The needle cannula is preferably thin-walled, while the hub is preferably lightweight. The stylet shaft conveniently bears on it a marking spaced from its distal end a distance equal to the length of the needle cannula. The marking can be inked or burnished.
In a second aspect, the present invention is directed to a medical device comprising at least a localizer stylet, the stylet comprising: a shaft comprising first and second wire segments each including respective distal ends and respective distal twisted portions adjacent their respective distal ends, the distal twisted portions being twisted twice about one another; the first wire segment further including a generally straight portion extending proximally of its distal twisted portion, and the second wire segment further including a hook extending proximally of its distal twisted portion; a rounded portion over the distal ends of the first and second wire segments; a needle assembly dimensioned to receive the localizer stylet therethrough; and a syringe connectable to the needle assembly; wherein the hook is straight and is angled away from the generally straight portion of the first wire segment; wherein the first and second wire segments are separate pieces and are composed of stainless steel wire having a circular cross-section; wherein the rounded portion comprises solder; and wherein the stylet shaft bears on it a marking spaced from its distal end a distance equal to the length of the needle cannula of the needle assembly.
In another aspect, the present invention is directed to a hookwire-type localizer stylet having a wire shaft with a distal end, and a hook depending from the wire shaft, the improvement wherein the hook is spaced proximally of the distal end of the wire shaft and wherein the wire shaft is twisted between the hook and its distal end.
Other embodiments include a pair of second wire segments extending proximally to respective diverging barbs, and the barb ends can be pointed r beveled to improve anchoring; and a pair of second wire segments twisted about the first with proximal ends diverging to respective ends and also distal ends diverging to respective ends, for anchoring against stress in both directions.
As indicated above, the medical device of the present invention possesses significant advantages over prior devices. It possesses the relative simplicity of construction and use enjoyed by prior Kopans-type or hookwire-type localizers and stylets. At the same time, the potential for breakage at the tip of its stylet is avoided. Moreover, the stylet of the medical device of the present invention is less subject to undesirable changes in position which might otherwise occur during patient transport or movement between the time of the performance of the localization procedure and the time of surgery.